Eventual Consistency document overhaul

Addresses issue #225 by tearing everything out and starting over.

Parts of the original document were simply wrong, and any document on eventual consistency that dives to a level where try-try-try is referenced is probably the wrong level of abstraction for the docs site, at least until we introduce a "really truly advanced" category of document.

I think this document can be expanded to cover more use cases/failure scenarios, but I think it gives a good idea of how things work without overwhelming the reader. I think. Feedback is welcome.